Several devices and nozzles for a fine atomization of fluids or suspensions are known from the patent literature.
From WO 91/14468 it is known to produce a spray of droplets by forcing a fluid through a small opening under high pressure.
Further, EP-A1-0 520 571 discloses an atomising nozzle for providing a spray of droplets comprising an orifice having a closure member movable between a position, in which it closes the orifice and a position spaced herefrom to define a gap. Under the action of pressurised fluid, the closure member is displaced relative to the orifice to define the gap, whereby a fluid film flows through the gap and breaks into droplets.
Moreover, from WO 92/19383 it is known to atomise a stream of fluids into droplets by said stream impinging a body placed in the discharge path at great velocity.
Finally EP-A2-0 387 179 discloses an atomising device, in which pressurised fluid is discharged through a vibrating-type atomising nozzle comprising a seat part having an outlet opening and a closing element biassed towards a closed position by means of a spring, in which it closes the outlet opening. By means of an electromechanical drive means the closing element may be oscillated between a closed and opened position relative to the seat part, whereby the pressurised fluid will be discharged from the outlet opening, when the closing element is in its open position.
Within the pharmaceutical field it is known to administer a medicament in solution or suspension as a fine spray through the nose or mouth. For inhalation purposes, the droplets of the spray have to be so small, i.e. about 10 micrometer or less, that they may be extrained by the inhaled air and reach their destination, i.e. the outer most alveoli in the lungs.
In order to obtain sufficiently small droplets, it has been the practice for many years to atomise the medicament in solution or suspension by means of a propellant usually of the freon-type. For environmental reasons and due to the physiological effect it is desirable to avoid the use of more or less inert propellants.